[Users] [Commits] [svn:einsteintoolkit] Paper_EinsteinToolkit_2010/examples/bbh/ (Rev. 85)

Erik Schnetter schnetter at cct.lsu.edu
Wed May 11 13:00:37 CDT 2011

That is strange. I assume some other routine overwrites it. Can you
check the schedule? Is there another CarpetMask or CarpetReduce
routine acting on the mask afterwards?


On Wed, May 11, 2011 at 1:30 PM, Bruno C. Mundim <bcmsma at astro.rit.edu> wrote:
> Thanks, Erik! On a related note: I checked if CarpetMask was setting
> weight[ind]=0 inside the horizons and it seems to do so correctly.
> However CarpetReduce::weight still do not reflect that. Its output
> still doesn't have the horizons masked out.
> Thanks,
> Bruno.
> Erik Schnetter wrote:
>> On Wed, May 11, 2011 at 12:53 PM, Bruno C. Mundim <bcmsma at astro.rit.edu>
>> wrote:
>>> Hi Roland:
>>> Roland Haas wrote:
>>>> Hello Bruno,
>>>>>  a) Its evolution is stopped with Nans around 8.6M. Nans appear to come
>>>>>  from the BSSN fields, but still needs further investigation.
>>>> Hmm I could evolve the qc0 example in McLachlan. Maybe there are
>>>> differences in the parameter file that make the error "obvious".
>>> A few obvious changes that I can think of:
>>> 1) I reduced the number of spherical surfaces from 5 to 3. Now the
>>> puncture tracker uses surfaces 0 and 1, AHFinderDirect track those
>>> surfaces and load AH related info there. QLM, CarpetTracker and
>>> CarpetMask uses those 2 surfaces then. I will go back to 5 surfaces
>>> as it was set before. Maybe I am missing some subtle scheduling order
>>> here. I don't know.
>>> 2) I added a few general parameters I am used to use to CarpetInterp,
>>> CarpetLib and CarpetRegrid2.
>>> 3) From a discussion I had with Peter on the ET workshop, I decided
>>> to change the AHFinderDirect interpolator to Hermite.
>>> So I will switch back to what it was and avoid to do so many changes
>>> at once! :) However I find strange that these changes could be the
>>> cause of what I am seeing.
>>>>>  c) When CarpetReduce::weight is output, its values seem strange to me.
>>>>>  Most of the domain has 1/2 set. A few points close to the boundary 1/4
>>>>>  and the boundaries 0 (physical and ghost). No mask out values inside
>>>>>  AH is shown, ie they still are set to 1/2. These values seem to make
>>>>>  more sense to AMR restriction operations.
>>>> Are you maybe looking at the z=0 plane? That plane has a weight of 1/2
>>>> since only half of the volume of each cell is used when eg. computing
>>>> the simulation volume. I have never used CarpetMask myself (but have
>>>> written a similar thorn of my own... would have paid to look into Carpet
>>>> first I guess :-) )
>>> Yes I was looking at the z=0 plane and had refection symmetry set up!
>>> Thanks for pointing this out. If we go out of the plane then the
>>> weight=1.0 values show up. A more careful look into the data, I noticed
>>> the zeros are set in the buffer zones indeed with the exception of the
>>> third point (ghostzone=3) in the domain (from the AMR boundary) that has
>>> its value set to 1/4. Do you know why?
>> For some reason that I currently cannot recall, the ghost zones in the
>> mask may be set to 1 instead of 0. However, ghost zones are ignored
>> anyway by a different mechanism when reducing (by using cctk_bbox and
>> cctk_nghostzones).
>> The particular values indicate how much of the "control cell"
>> surrounding this grid point should be taken into account when
>> reducing. If the value is 1/4, then you may be looking at an edge
>> point (e.g. and x-y edge in the z=0 plane), where 3/4 of the control
>> cell are already covered by the corresponding coarse grid.
>> One important test is that the sum of all weights times the grid cell
>> volume equals the total volume of the simulation domain. If you look
>> into the simulation log output and search for "volume" there, you
>> should find a corresponding statement.
>> -erik

Erik Schnetter <schnetter at cct.lsu.edu>   http://www.cct.lsu.edu/~eschnett/

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